A professional brewer friend once told me that, for him, the American sour-beer renaissance has been like being confined to a brewhouse his entire life, knowing no different, and then throwing open a window to glimpse a bright, wild, vibrant world filled with possibility and ripe for exploration. And yet many beer drinkers, having tried a sour or three, tend to limit their expectations to a very narrow view.
In reality, sours are a broad-reaching category that encompasses a breadth of styles and brewing techniques—from historic lambics and other traditional Belgian and German brews to today’s Wild West of experimental sours and wild ales—as well as a wide range of flavors and intensity.
The Science of Sour
Many sour beers are fermented, in full or in part, using a strain of Brettanomyces. Brettanomyces, or Brett for short, is a wild cousin of domesticated brewer’s yeast that was first discovered growing on fruit skins. Winemakers consider it a spoiling agent and go to great lengths to keep it from contaminating their cellars, but sour-beer brewers have embraced it. It’s especially good at chopping up long chains of sugars that Saccharomyces won’t eat and converting those sugars into alcohol and CO2. Brett also imparts a wide range of esters and phenols—often described as earthy, fruity, musty, or funky depending on the specific strain used. These rustic, wild flavors go a long way toward giving sour beers their character, but _Brett _isn’t what makes a beer sour.